the only way I can think this may be possible is in the Macropump, run a check in the Macropump code to check the current position DRO and if its greater than 700 drop the speed, the down side to this is it would do it for every program that travelled over 700mm so you would have to edit it out once the job was complete.

Thanks for your answer, I do not know how to do this in macropump, I will investigate on how to do it, if you could pass me some tutorials about how to proceed I would appreciate it.

My problem really is that I would need to decrease the velocity of spindle gradually as the speed of the machine goes down (feed rate). Maybe it's easier to set something up this way? Do you know if it is possible?

Dan,Lots of people try to use Mach for a custom machine because the thinking is that if it can control a CNC machine then it should be easy and cheap to use it here. Nearly everyone winds up where you are, some little tweak you need but can't do. Figure in the cost of the PC and keeping it running and the cost is way higher than you realize.

However there is a really good answer now for what you are trying to do. You need to use an Automation Direct DoMore BRX plc. You can get them with up to 8 high speed outputs to control stepper or servo at up to 250Kz step rate. Lots of digital IO. Up to 4 channels analog inputs and 2 channels of analog output on the base module. Expansion modules available of all kinds. The BRX has a ton of motion commands and can do what you need easily. Programming is via DoMore Designer ladder logic software which is FREE. Phone tech support is excellent and FREE. Has ethernet, serial, modbus communications and can do email and talk to anything.

I use them at work, and just installed one in my homebuilt CNC so that I can get control of my lathe spindle running on a large stepper motor, which Mach can't do, plus controlling the heat for the 3D printer extruder, and the heated build plate, and analog output to my DC mill spindle controller.

Hi Gary, thanks for your response. To use a PLC is something I already thought might be necessary for my machine. But always thinking of a cnc control software with a built-in PLC, I never thought of doing it all by PLC. The fact is that I have researched a little about this system that you have recommended me and I do not find anything about how it would work as cnc, that is, the G code would no longer be used but then, you can't use softwares for create and editing the codes from a design. So how do you create the coordinates of movement? The whole process is manual? Is not this much more complicated?

Dan,You didn’t say much about what the machine does or how many axis etc. Years ago I built watering/spraying robots for commercial greenhouses. We tried to use a PC as HMI with a PLC controlling everything. We constantly had problems on the PC side and I finished the job in the PLC alone. Still running 20 years later!

I faced the same problem and created a G-code. Short for Growbot which is what we called the machine. The PLC read two digit codes and four digit data entered by the operator and then the PLC performed the appropriate task. The BRX has the advantage of an SD card that can be programmed off line and has huge capacity. Also using something called stage programming you can simply read a line for the G-code and jump to a stage that performs that task. Create only those codes you need and also the special ones no CNC program would have, like what you are trying to do.

You may only need a few G-codes because a CAM program like CamBam could create everything your machine needs from just some basic codes. G-code has been around for a long time and lots of the codes were useful when the machine had no memory and programming was done by hand. With CAM many codes are no longer needed.

You might want to look at a C-More HMI. That would connect to the PLC and give you every pushbutton, selector, and slider needed. It also has a recipe function that can store a sequence of steps. A recipe could even be a file selection on the SD card containing the program to use. A C-more does data logging and trending to get data on what you produced. It also has web server and you can see and run your machine from a connected PC or using a $5 app from your cell phone!